Remember that many instructions set flags according to their result, obviating the need for an explicit test before the conditional jump.
22.
For example, a common code sequence like a compare followed by a conditional jump would become a single micro-op.
23.
Conditional jumps that are taken every second time or have some other regularly recurring pattern are not predicted well by the saturating counter.
24.
Conditional jumps are taken ( execution continues at another address ) or not ( execution continues at the next instruction ) depending on some condition.
25.
When the code for a conditional jump is read we do not yet know the next instruction to execute and insert into the execution pipeline.
26.
The conditional jump instructions are listed in pairs, the former opcode is for a forward jump, and the latter one for a backward jump.
27.
There are three main classes of instruction : arithmetic, logical, and move; conditional jump; conditional skip ( which may have side effects ).
28.
The branch predictor attempts to avoid this waste of time by trying to guess whether the conditional jump is most likely to be taken or not taken.
29.
The stack was flushed by an unconditional jump instruction, so unconditional jumps at the ends of loops were conventionally written as conditional jumps that would always succeed.
30.
The branch predictor may, for example, recognize that the conditional jump is taken more often than not, or that it is taken every second time.
